Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1281016299-23958-15-git-send-email-andrea.gelmini@gelma.net>
Signed-off-by: NAndrea Gelmini <andrea.gelmini@gelma.net>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Only in verbose mode so as not to bloat struct symbol too much.

The key used is '/', just like in vi, less, etc.

More work is needed to allocate space on the symbol in a more clear way.

This experiment shows how to do it for the hist_browser, in the main
window.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

By using BITS_PER_LONG/4 as the width specifier.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Otherwise entries will get chopped up on the window.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Press -> and then "Browse map details" to see the DSO long name as the title
and the list of symbols in the DSO used by the map where the current symbol is.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

So that tools that wan't to act only on a subset of (weak, global,
local) symbols can do so, such as the upcoming uprobes support in 'perf
probe'.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

The event__process function is useful in processing /proc/<pid>/maps.  All of
the functions that are called from event__process are defined in util/event.c.
Though its defined in builtin-top.c, it could be reused for perf probe for
uprobes. Hence moving it to util/event.c and exporting the function.

LKML-Reference: <20100802123851.GD22812@linux.vnet.ibm.com>
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Fix buggy-looking code which unnecessarily adjusts the file offset
fields read from /proc/*/maps.

This may have gone unnoticed since the offset is usually 0 (and the
logic in util/symbol.c may work incorrectly for other offset values).

Commiter note:

This fixes a bug introduced in 4af8b35d, there is no need to shift pgoff
twice, the show_map_vma routine in fs/proc/task_mmu.c already converts
it from the number of pages to the size in bytes, and that is what
appears in /proc/PID/map.

Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Will Deacon <Will.Deacon@arm.com>
LKML-Reference: <1280836116-6654-2-git-send-email-dave.martin@linaro.org>
Signed-off-by: NDave Martin <dave.martin@linaro.org>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

For a file with:

[root@emilia linux-2.6-tip]# perf report -D -fi allmodconfig-j32.perf.data | grep events:
     TOTAL events:      36933
      MMAP events:       9056
      LOST events:          0
      COMM events:       1702
      EXIT events:       1887
  THROTTLE events:          8
UNTHROTTLE events:          8
      FORK events:       1894
      READ events:          0
    SAMPLE events:      22378
      ATTR events:          0
EVENT_TYPE events:          0
TRACING_DATA events:          0
  BUILD_ID events:          0
[root@emilia linux-2.6-tip]#

Testing with valgrind and making perf_session__delete() a nop, so that
we can notice how many maps were actually deleted due to not having any
samples on it:

==== HEAP SUMMARY:

Before:

==10339==     in use at exit: 8,909,997 bytes in 68,690 blocks
==10339==   total heap usage: 78,696 allocs, 10,007 frees, 11,925,853 bytes allocated

After:

==10506==     in use at exit: 8,902,605 bytes in 68,606 blocks
==10506==   total heap usage: 78,696 allocs, 10,091 frees, 11,925,853 bytes allocated

I.e. just 84 detected unmaps with no hits out of 9056 for this workload,
not much, but in some other long running workload this may save more
bytes.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

If we receive two PERF_RECORD_EXIT for the same thread, we can end up
reusing session->last_match and trying to remove the thread twice from
the rb_tree, causing a segfault, so invalidade last_match in
perf_session__remove_thread.

Receiving two PERF_RECORD_EXIT for the same thread is a bug, but its a
harmless one if we make the tool more robust, like this patch does.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Which is at perf_session__destroy_kernel_maps, counterpart to the
perf_session__create_kernel_maps where the kmap structure is located, just
after the vmlinux_maps.

Make it also check if the kernel maps were actually created, which may not
be the case if, for instance, perf_session__new can't complete due to
permission problems in, for instance, a 'perf report' case, when a
segfault will take place, that is how this was noticed.

The problem was introduced in d65a458b, thus post .35.

This also adds code to release guest machines as them are also created
in perf_session__create_kernel_maps, so should be deleted on this newly
introduced counterpart, perf_session__destroy_kernel_maps.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

So that we reduce the noise when looking for leaks using tools such as
valgrind.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

For long running sessions with many threads with short lifetimes the
amount of memory that the buildid process takes is too much.

Since we don't have hist_entries that may be pointing to them, we can
just release the resources associated with each thread when the exit
(PERF_RECORD_EXIT) event is received.

For normal processing we need to annotate maps with hits, and thus
hist_entries pointing to it and drop the ones that had none. Will be
done in a followup patch.

Cc: David S. Miller <davem@davemloft.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

As a precursor for perf to support uprobes, rename fields/functions
that had kprobe in their name but can be shared across perf-kprobes
and perf-uprobes to probe.

Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Wielaard <mjw@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Naren A Devaiah <naren.devaiah@in.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20100729141351.GG21723@linux.vnet.ibm.com>
Signed-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Changes:
	* Simplification of the main search loop on dso__load()
	* Replace the search with a 2-pass search:
		* First, try to find an image with a proper symtab.
		* Second, repeat the search, accepting dynsym.

A second scan should only ever happen when needed debug images are
missing from the buildid cache or stale, i.e., when the cache is out of
sync.

Currently, the second scan also happens when using separated debug
images, since the caching logic doesn't currently know how to cache
those.  Improvements to the cache behaviour ought to solve that.
Signed-off-by: NDave Martin <dave.martin@linaro.org>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Signed-off-by: NDave Martin <dave.martin@linaro.org>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

If we have a buildid, then we never want to load an image which has no buildid,
or which has a different buildid, so it makes sense for the check to be built
into dso__load and not done separately.  This is fine for old distros which
don't use buildid at all since we do no check in that case.

This refactoring also alleviates some subtle race condition issues by not
opening ELF images twice to check the buildid and then load the symbols, which
could lead to weirdness if an image is replaced under our feet.
Signed-off-by: NDave Martin <dave.martin@linaro.org>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Tidy-up patch to remove some code and struct perf_session data members
which are no longer needed due to the previous patch: "perf tools: Don't
abbreviate file paths relative to the cwd".

LKML-Reference: <new-submission>
Signed-off-by: NDave Martin <dave.martin@linaro.org>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

This avoids around some problems where the full path is executables and DSOs it
needed for finding debug symbols on platforms with separated debug symbol files
such as Ubuntu.  This is simpler than tracking an extra name for each image.

The only impact should be that paths in verbose output from the perf tools
become absolute, instead of relative to .

LKML-Reference: <new-submission>
Signed-off-by: NDave Martin <dave.martin@linaro.org>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

The stock newt checkbox tree widget we were using was not really
suitable for hist entry + callchain browsing.

The problems with it were manifold:

- We needed to traverse the whole hist_entry rb_tree to add each entry +
  callchains beforehand.

- No control over the colors used for each row

So a new tree widget, based mostly on slang, was written.

It extends the ui_browser class already used for annotate to allow the
user to fold/unfold branches in the callchains tree, using extra fields
in the symbol_map class that is embedded in hist_entry and
callchain_node instances to store the folding state and when changing
this state calculates the number of rows that are produced when showing
a particular hist_entry instance.

This greatly speeds up browsing as we don't have to upfront touch all
the entries and only calculate callchain related operations when some
callchain branch is actually unfolded.

The memory footprint is also reduced as the data structure is not
duplicated, just some extra fields for controling callchain state and to
simplify the process of seeking thru entries (nr_rows, row_offset) were
added.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

So that we gain two columns and look more like classical (at least in
TUIs) scroll bars bars.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

When we call ui_browser__show we may have called
ui_browser__refresh_dimensions to check if the maximum lenght for the
contained entries changed, such as when zooming in and out DSOs or
threads in the hist browser.

For that to happen we must delete the old form, that will take care of
deleting the vertical scrollbar, etc, and then recreate them, with the
new dimensions.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Will be used to figure out the window width needed in the new tree
widget.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

They were globals, and since we support multiple hists and sessions
at the same time, it doesn't make sense to calculate those values
considereing all symbols in all sessions.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

And don't consider them in hists__inc_nr_entries.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

When parsing the objdump disassembly output we can have goto labels that
are valid hex numbers and thus get confused with lines with machine
code.

Handle the common case of a label that has nothing after it and other
cases where there is just source code by validating the resulting "ip".

It is still possible that we find goto labels that are in the function
address range, but only if they are located before the real address we
should be OK.

A change in the objdump output to have a clear marker separating
addresses from the disassembly would come handy, but we would still have
to deal with older versions.
Reported-by: NGleb Natapov <gleb@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <20100722170541.GF17631@ghostprotocols.net>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Introducing hists__remove_entry_filter.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Right now ENTER doesn't always exits the newt tree widget, as it is used
for expanding/collapsing branches, but with the new tree widget being
developed we need to regain control to handle it, expanding/collapsing
branches.

In fact its really up to the ui_browser user to state what extra keys
should stop ui_browser__run, and it should handle just the ones needed
for basic browsing.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

When I ran "perf kvm ... top", I encountered the following error output.

  Error: perfcounter syscall returned with -1 (Too many open files)

  Fatal: No CONFIG_PERF_EVENTS=y kernel support configured?

Looking into perf, I found perf opens too many directories at
initialization time, but forgets to close them. Here is the fix.

LKML-Reference: <4C230362.5080704@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Invert the return value of die_compare_name(), because it returns a 'bool'
result which should be expeced true if the die's name is same as compared
string.

LKML-Reference: <4C36EBED.1000006@hitachi.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Gcc generates DW_AT_comp_dir and stores relative source path if building kernel
without O= option. In that case, perf probe --line sometimes doesn't work
without --source option, because it tries to access relative source path.

This adds DW_AT_comp_dir support to perf probe for finding an absolute source
path when no --source option.

LKML-Reference: <4C36EBE7.3060802@hitachi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Perf probe -L shows incorrect error message (Dwarf error) if it fails to find
source file. This can confuse users.

# ./perf probe -s /nowhere -L vfs_read
Debuginfo analysis failed. (-2)
  Error: Failed to show lines. (-2)

With this patch, it shows correct message.

# ./perf probe -s /nowhere -L vfs_read
Failed to find source file. (-2)
  Error: Failed to show lines. (-2)

LKML-Reference: <4C36EBDB.4020308@hitachi.com>
Cc: Chase Douglas <chase.douglas@canonical.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: NChase Douglas <chase.douglas@canonical.com>
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Hists that have been filtered, because they don't have callchains
matching the parent filter, won't be printed. As such,
hist_entry__snprintf() returns 0 for them, but we don't control
this value and we always print the buffer, which might be
untouched and then only made of random stack garbage.

Not only does it paint the screen with barf, it also prints
the callchains for these hists, even though they have been filtered,
since the hist has been filtered as well.

We need to check the return value of hist_entry__snprintf() and
ignore the hist if it is 0, which means it didn't get any callchain
matching the parent filter. This fixes the barf and the undesired
callchains.
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>

Hists have their hits increased by the event period. And this
period based counting is the foundation of all the stats in
perf report.

But callchains still use the raw number of hits, without taking
the period into account. So when we compute the percentage,
absolute based percentages are totally broken, and relative ones
too in the first parent level. Because we pass the number of events
muliplied by their period as the total number of hits to the
callchain filtering, while callchains expect this number to be
the number of raw hits.

perf report -g graph was simply not working, showing no graph unless
the min percent was zero. And even there the percentage of the
branches was always 0. And may be fractal filtering was broken on
the first branch level too.

flat also was broken, but it was hidden because of other breakages.

Anyway fix this by counting using periods on callchains.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>

Initialize the callchain radix tree root correctly.

When we walk through the parents, we must stop after the root, but
since it wasn't well initialized, its parent pointer was random.

Also the number of hits was random because uninitialized, hence it
was part of the callchain while the root doesn't contain anything.

This fixes segfaults and percentages followed by empty callchains
while running:

	perf report -g flat
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: 2.6.31.x-2.6.34.x <stable@kernel.org>